Final answer:
A segment is not an undefined term in geometry; it can be defined using points and is thus the correct answer to the question.
Step-by-step explanation:
The question is asking which of the given options is not an undefined term in geometry. An undefined term is a basic idea that cannot be defined by other terms but is instead explained using examples and properties. In geometry, the three undefined terms are point, line, and plane.
These terms are the building blocks of geometry and are foundational concepts that are accepted without definition. On the other hand, a segment, which is part of a line that is bounded by two distinct end points, can be defined using the concept of points. Therefore, the answer to the question is d) Segment, which is not an undefined term.
In geometry, all of the terms listed (point, line, plane, segment) are undefined terms. This means that they are not defined using other geometric terms, but are instead fundamental concepts that are accepted without definition. So, the correct answer is none of the above.
Therefore answer is a) Point.